oops very sad to see them.
I think some can still be rescued.
First, cut off blacken, mushy leaves & stem using sterilize blade. When cutting stem, trim down till you no longer see back area. Then seal up each wound using cinnamon or fungicide paste.
After this operation, spray all these plant with fungicide thoroughly. Repeat every three days or so for about 3 weeks or so. You can either mount or pot them. But I prefer mounting them.
Then, keep them under bright light with good air-circulation. Don't put under direct sunlight as this will stress to them.
When you see them establish on mount, you can slowly introduce them to direct morning sunlight. Start fertilizing them once established on mount.
Hope this helps.